#include "abl/string/encoding/utf8.hpp"
#include "abl/string/string.hpp"

#include <assert.h>

namespace abl 
{


  const char* utf8_encoding_c::_names[] =
    {
      "UTF-8",
      "UTF8",
      NULL
    };


  const text_encoding_c::CharacterMap utf8_encoding_c::_charMap = 
    {
      /* 00 */	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 
      /* 10 */	0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 
      /* 20 */	0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 
      /* 30 */	0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 
      /* 40 */	0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f, 
      /* 50 */	0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f, 
      /* 60 */	0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, 
      /* 70 */	0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f, 
      /* 80 */	  -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1, 
      /* 90 */	  -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1, 
      /* a0 */	  -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1, 
      /* b0 */	  -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1, 
      /* c0 */	  -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2, 
      /* d0 */	  -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2, 
      /* e0 */	  -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3, 
      /* f0 */	  -4,   -4,   -4,   -4,   -4,   -4,   -4,   -4,   -5,   -5,   -5,   -5,   -6,   -6,   -1,   -1, 
    };


  utf8_encoding_c::utf8_encoding_c()
  {
  }


  utf8_encoding_c::~utf8_encoding_c()
  {
  }


  const char* utf8_encoding_c::canonicalName() const
  {
    return _names[0];
  }


  bool utf8_encoding_c::isA(const std::string& encodingName) const
  {
    for (const char** name = _names; *name; ++name)
      {
	if (abl::icompare(encodingName, *name) == 0)
	  return true;
      }
    return false;
  }


  const text_encoding_c::CharacterMap& utf8_encoding_c::characterMap() const
  {
    return _charMap;
  }


  int utf8_encoding_c::convert(const unsigned char* bytes) const
  {
    int n = _charMap[*bytes];
    int uc;
	
    switch (n)
      {
      case -6:
      case -5:
      case -1:
	return -1;
      case -4: 
      case -3: 
      case -2:
	if (!isLegal(bytes, -n)) return -1;
	uc = *bytes & ((0x07 << (n + 4)) | 0x03);
	break;
      default:
	return n;
      }

    while (n++ < -1) 
      {	
	uc <<= 6;
	uc |= (*++bytes & 0x3F);
      }
    return uc;
  }


  int utf8_encoding_c::convert(int ch, unsigned char* bytes, int length) const
  {
#ifdef _DEBUG
    unsigned char* lb = bytes;
#endif

    if (ch <= 0x7F)
      {
	if (bytes && length >= 1)
	  *bytes = (unsigned char) ch;
	return 1;
      }
    else if (ch <= 0x7FF)
      {
	if (bytes && length >= 2)
	  {
	    *bytes++ = (unsigned char) (((ch >> 6) & 0x1F) | 0xC0);
	    *bytes   = (unsigned char) ((ch & 0x3F) | 0x80);
	  }
#ifdef _DEBUG
	assert (isLegal(lb, 2));
#endif
	return 2;
      }
    else if (ch <= 0xFFFF)
      {
	if (bytes && length >= 3)
	  {
	    *bytes++ = (unsigned char) (((ch >> 12) & 0x0F) | 0xE0);
	    *bytes++ = (unsigned char) (((ch >> 6) & 0x3F) | 0x80);
	    *bytes   = (unsigned char) ((ch & 0x3F) | 0x80);
	  }
#ifdef _DEBUG
	assert (isLegal(lb, 3));
#endif
	return 3;
      }
    else if (ch <= 0x10FFFF)
      {
	if (bytes && length >= 4)
	  {
	    *bytes++ = (unsigned char) (((ch >> 18) & 0x07) | 0xF0);
	    *bytes++ = (unsigned char) (((ch >> 12) & 0x3F) | 0x80);
	    *bytes++ = (unsigned char) (((ch >> 6) & 0x3F) | 0x80);
	    *bytes   = (unsigned char) ((ch & 0x3F) | 0x80);
	  }
#ifdef _DEBUG
	assert (isLegal(lb, 4));
#endif
	return 4;
      }
    else return 0;
  }


  int utf8_encoding_c::queryConvert(const unsigned char* bytes, int length) const
  {
    int n = _charMap[*bytes];
    int uc;
    if (-n > length)
      {
	return n;
      }
    else
      {
	switch (n)
	  {
	  case -6:
	  case -5:
	  case -1:
	    return -1;
	  case -4:
	  case -3:
	  case -2:
	    if (!isLegal(bytes, -n)) return -1;
	    uc = *bytes & ((0x07 << (n + 4)) | 0x03);
	    break;
	  default:
	    return n;
	  }
	while (n++ < -1) 
	  {	
	    uc <<= 6;
	    uc |= (*++bytes & 0x3F);
	  }
	return uc;
      }
  }


  int utf8_encoding_c::sequenceLength(const unsigned char* bytes, int length) const
  {
    if (1 <= length)
      {
	int cc = _charMap[*bytes];
	if (cc >= 0)
	  return 1;
	else
	  return -cc;
      }
    else return -1;
  }


  bool utf8_encoding_c::isLegal(const unsigned char *bytes, int length)
  {
    // Note: The following is loosely based on the isLegalUTF8 function
    // from ftp://ftp.unicode.org/Public/PROGRAMS/CVTUTF/ConvertUTF.c
    // Excuse the ugliness...
	
    if (0 == bytes || 0 == length) return false;

    unsigned char a;
    const unsigned char* srcptr = bytes + length;
    switch (length)
      {
      default:
	return false;
	// Everything else falls through when true.
      case 4:
	if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;
      case 3: 
	if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;
      case 2:
	if ((a = (*--srcptr)) > 0xBF) return false;
	switch (*bytes) 
	  {
	  case 0xE0:
	    if (a < 0xA0) return false; 
	    break;
	  case 0xED:
	    if (a > 0x9F) return false; 
	    break;
	  case 0xF0:
	    if (a < 0x90) return false; 
	    break;
	  case 0xF4:
	    if (a > 0x8F) return false; 
	    break;
	  default:
	    if (a < 0x80) return false;
	  }
      case 1:
	if (*bytes >= 0x80 && *bytes < 0xC2) return false;
      }
    return *bytes <= 0xF4;
  }


} // namespace abl
